class Solution {
    public String modifyString(String ss) {
        char[] s=ss.toCharArray();
        int n=s.length;
        for(int i=0;i<n;i++){
            if(s[i]=='?'){
                for(char ch='a';ch<='z';ch++){
                    if((i==0||s[i-1]!=ch)&&(i==n-1||s[i+1]!=ch))
                        s[i]=ch;
                }
            }
        }
        return String.valueOf(s);
    }
}